Vegetation versus Flora

Transcription

1 What lives where and why? Ecological hypotheses Do the species occur here because of similar climate? latitude? animal grazing? montane rain shadows? fire history? Australian grass savanna African grass savanna

2 What lives where and why? Ecological hypotheses These hypotheses and questions examine environmental stresses on species to produce these characteristic vegetation types, physiognomy, or life forms Convergent adaptation or evolution operating? Australian grass savanna African grass savanna

3 What lives where and why? Historical hypotheses Are the species occurring in both areas related? Has there been long distance dispersal between the two areas? Areas related geologically - once sharing a common biota? Australian grass savanna African grass savanna

4 What lives where and why? Historical hypotheses These hypotheses and questions are interested in the flora (actual species composition) and history of the both the species and the areas they inhabit Australian grass savanna African grass savanna

5 Similarity of Australian and African grass savannas largely explained by ecological answers Both have Acacia as the dominant small tree and grasses as the dominant herbs, but the species are unrelated Australian grass savanna African grass savanna

6 Do species occurring in Mediterranean biomes (5 of them) look similar because of ecological similarity or because they are floristically similar?

7 Do species occurring in Mediterranean biomes (5 of them) look similar because of ecological similarity or because they are floristically similar? Because of the severe alternation of winter rain and summer aridity? Because of cold ocean currents flowing from high latitudes on west sides of continents?

8 Do many species have holly leaves because they are closely related? or, because tough leathery leaves, with spine tips are an adaptation to the Mediterranean climate? Convergent evolution! Ilex (Aquifoliaceae) holly Quercus ilex (Fagaceae) Banksia ilicifolia (Proteaceae)

9 Does mountain sweet cicely have this amphitropical distribution because ecological conditions are similar in all three areas? or long distance dispersal? or previous continental connections? Osmorhiza chilensis Mountain sweet cicely Apiaceae

10 Are these amphi-atlantic species pairs simply ecological replacements? or are they closely related species separated by a now expanding North Atlantic ocean? A B A B white oak beech basswood A B ash

11 Alexander von Humboldt ( ) First naturalist to make explicit distinction between vegetation and flora and connection between climate and plant distributions Funeral in 1859 was one of the greatest the city of Berlin ever saw What did he do that was so special?

12 1799 left for Latin America with Aine Bonpland for 6 years landed in Venezuela and visited Cuba, Colombia, Ecuador, Peru, and Mexico studied flora, fauna, geology, meterology, ocean currents

13 Epidendrum ibaguense H.B.K. Vegetation versus Flora made first plant collections for the area - many new species with H.B.K. authority designation traversed the Upper Orinoco in southern Venezuela, documenting its unusual flow Cinchona - quinine

14 made first plant collections for the area - many new species with H.B.K. authority designation traversed the Upper Orinoco in southern Venezuela, documenting its unusual flow wrote extensively on indigenous inhabitants for the first time

15 most notable writings include Essays on the Geography of Plants (1805) 1. Observations on the effect of altitudinal differences on vegetation Cerro Avila, north of Caracas, first mountain zoned

16 most notable writings include Essays on the Geography of Plants (1805) 1. Observations on the effect of altitudinal differences on vegetation Chimborazo, Ecuador (1.5 S; 20,703ft - 6,310m)

17 most notable writings include Essays on the Geography of Plants (1805) 1. Observations on the effect of altitudinal differences on vegetation Chimborazo, Ecuador (1.5 S; 20,703ft - 6,310m) Earth is an oblate sphere radius at equator 22km larger than at poles Chimborazo is 2km further from center of earth than Mt. Everest

18 most notable writings include Essays on the Geography of Plants (1805) 1. Observations on the effect of altitudinal differences on vegetation Chimborazo, Ecuador (1.5 S; 20,703ft - 6,310m) e.g., at 1,950m left savannas and entered sclerophyllous shrub vegetation belt (ericads - Ericaceae or blueberry family)

19 2. Compilation of species for both South America and Eurasia (floristics) Demonstrated sclerophyllous shrub belt is found in Andes, Himalayas, and Alps, and often dominated by Ericaceae, but different genera and species! Vegetation versus Flora

20 The substitution, or the repetition, of similar, almost identical morphological types in different regions separated from each other by oceans or wide areas of land, is a marvelous law of nature von Humboldt Vegetation versus Flora Even if nature does not produce the same species in similar climates, nevertheless the vegetation exhibits the most striking visual similarities in habit even in the most distant regions. This phenomenon is one of the most remarkable in the history of organic creations same vegetation not same flora implies convergent evolution!

21 Each plant community consists of a definite group of life forms. Each habitat favors certain groups of life forms and almost excludes others. The more extreme the habitat conditions the sharper the selection and the more pronounced are the ecological characteristics of the life forms. Josias Braun-Blanquet, 1932

22 Quite apart from the influence of climates in the distribution of individual plant species, climate strikes at the structure of vegetation everywhere in the same way, whatever its floristic composition. That is to say, similar climates in widely separated parts of the world induce the emergence of similar kinds of plant formations in the physiognomic sense. Pierre Dansereau, 1951

23 3. Reduced variety of plant life forms to 15 basic types - first of its kind Humboldt s life forms by latitude based on drawing of Ferdinand Cohn

24 The simplest and most well known classification of plant forms that disregards their systematics is that of the Danish botanist Raunkiaer (1934) Raunkiaer, C. (1934) The life forms of plants. Oxford University Press

25 The simplest and most well known classification of plant forms that disregards their systematics is that of the Danish botanist Raunkiaer (1934) He classified plants according to their life forms defined by the way in which these buds were held and protected Raunkiaer, C. (1934) The life forms of plants. Oxford University Press

26 Phanerophytes- trees and shrubs Epiphytes - plants growing on plants Chamaephytes - buds near ground level Hemicryptophytes - buds in leaf litter Cryptophytes - buds covered Geophytes - buds underground Helophytes - marsh plants Hydrophytes - aquatics Therophytes - annuals Raunkiaer life forms (based on position of perennating bud)

27 Distribution of Plant Life Forms in Various Biomes Phanero. (trees/ shrubs) Chamae. (near ground) Hemicrypto (leaf litter) Crypto. (under ground) Thero. (annuals) Rainforest 96% 2% 0% 2% 0% Desert 11% 7% 27% 14% 41% Temperate Deciduous Forest 15% 2% 49% 22% 12% Tundra 0% 23% 61% 15% 1%

28 Distribution of Plant Life Forms in Various Biomes Phanero. (trees/ shrubs) Chamae. (near ground) Hemicrypto (leaf litter) Crypto. (under ground) Thero. (annuals) Rainforest 96% 2% 0% 2% 0% Desert 11% 7% 27% 14% 41% Temperate Deciduous Forest 15% 2% 49% 22% 12% Tundra 0% 23% 61% 15% 1%